This invention relates to dental appliances and, more particularly, to gingival tissue retraction cords.
In dental therapeutics, it is often necessary to retract gingival tissue in order to prepare patients for taking impressions, setting crowns or effecting restorations.
In a widely used procedure for retracting gingival tissue, cotton cord, impregnated with a therapeutic preparation having astringent and hemostatic properties, is disposed about the tooth and placed into the gingival crevice for a limited time period to effect tissue displacement.
The fluid absorbent, cotton cord which is used in gingival retraction may be single or multiple strand of suitable cross-sectional area for dental purposes. The therapeutic preparations which may be absorbed onto the cotton cord to effect gingival retraction include, for example, racemic epinephrine hydrochloride and aluminum compounds such as potassium aluminum sulfate (alum). For a further discussion of gingival retraction with cotton cords as well as absorbent, resilient, circular rings composed of hard or soft leather, see U.S. Pat. No. 3,238,620 (Robertson, 1966).
Although the gingival retraction cord of the prior art is very effective as a tissue displacement device and agent, it has various negating characteristics. The mechanical handling of the prior art cord, which usually consists of twists of cotton strands or filaments has been somewhat difficult and awkward because of the pliable nature of the cord; in particular, it is difficult and awkward to thread the pliable cord between closely adjacent teeth and, where desired, to tie the loose ends prior to the insertion of the therapeutic cord into the gingival crevice. Also, unless the cord is packed into the gingival crevice with instrumentation which is applied in alignment with the twist, the strands or filaments can become unraveled during the packing step. The cotton twist cord may split during packing with the "L" shaped packing instrument whereby the horizontal arm of the instrument traverses the cord and reciprocal removal of the instrument through the body of the cord is somewhat difficult; and, in extreme cases, the traversal of the cotton twist cord by the relatively sharp packing instrument may result in severance of tooth attachment tissue. Since the cotton twist cord is highly pliable, it presents relatively small resistance to gum force and, while disposed in the gingival sulcus, it tends to flatten out thereby decreasing the spaced relationship between the tooth and the gum which can interfere with the taking of an impression. In addition, the tensile strength of the cotton twist cord is relatively weak as a result of which the cord tends to fray and leave therapeutically impregnated lint in the gingival sulcus which may cause tissue irritation.
Accordingly, the principal object of this invention is to provide a moderately firm, flexible, fluid absorbent, gingival retraction cord which (a) facilitates the circumdisposition of the cord about the tooth, (b) resists splitting during the packing of the cord into the gingival sulcus, (c) maintains its shape in the gingival sulcus and (d) is substantially fray resistant and lint free.